Study on synthesis of polycrystalline cubic boron nitride from hexagonal boron nitride by direct phase transition
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摘要: 以六方氮化硼为初始材料,采用直接转化法在9~15 GPa、1 500~2 100 ℃的条件下合成多晶立方氮化硼。采用X射线衍射仪、扫描电子显微镜、维氏硬度计,对多晶立方氮化硼块材的微观结构和力学性能进行表征。结果表明:在合适的温度、压力条件下,六方氮化硼可转化为纯相多晶立方氮化硼,其晶粒尺寸最小约为70 nm ,最大可达10 μm以上;在温度相同条件下,多晶立方氮化硼块材的晶粒尺寸随着合成压力的升高而减小,硬度随着合成压力的升高而增大,最高硬度可达64.45 GPa。Abstract: Polycrystalline cubic boron nitride was synthesized by direct phase transition at 9~15 GPa and 1 500~2 100 ℃ using hexagonal boron nitride as initial material. The microstructure and mechanical properties of polycrystalline cubic boron nitride bulk materials were characterized by X-ray diffractometer, scanning electron microscope and Vickers hardness tester. The results show that the pure phase polycrystalline cubic boron nitride can be prepared under suitable temperature and pressure with the minimum grain size about 70 nm and the maximum more than 10 μm. At the same temperature, the grain size of polycrystalline cubic boron nitride bulk decreases with the increase of synthesis pressure, and the hardness increases with the increase of synthesis pressure with the highest hardness 64.45 GPa.
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